Technical Field
The present invention relates to management of energy storage systems, and more particularly to management of energy storage systems to maximize PV-utilization and provide optimal charging and discharging while minimizing demand charge costs.
Description of the Related Art
Recently, growing penetration of rooftop PV generation is causing operational challenges for utility companies to keep the voltage within an acceptable range. Consequently, new studies have been focused on using behind-the-meter (BTM) battery energy storage systems (BESSs) to increase the local PV-utilization. However, a major obstacle in combining DC management and PV-utilization service lies in their opposing nature, namely that DC reduction works better when a BESS is fully charged and ready to shave the peak, while PV-utilization prefers a battery which is not fully charged and ready to store the excess generation. Studies have been performed regarding the influence of load patterns on PV-self consumption, but do not provide any type of controller mechanism for charging/discharging functions. A “delayed charging” algorithm has also been proposed to increase the state of charge (SOC) every 15-minutes in a linear fashion. However, in the case of, for example, peak shaving event in early hours, there is not enough energy stored in the battery using such conventional systems and methods. Another study has suggested using batteries and flexible loads to increase the PV utilization, but does not address the problem of DC management, controllable loads, or overall charging/discharging functions for BESSs.
Conventional rule-based controllers have been used to only discharge the battery when the grid power is higher than the DC threshold and fully charge the battery when the demand is lower than the DC threshold. Although this controller is successful in DC management, it is not able to capture the excess PV production and prevent curtailment. Moreover, conventional systems and methods lead to high average annual state of charge (SOC), which reduces the overall battery lifetime.